charnames(3)

NAME
charnames - define character names for "\N{named}" string literal escape.

SYNOPSIS
  use charnames ':full';
  print "\N{GREEK SMALL LETTER SIGMA} is called sigma.\n";
  use charnames ':short';
  print "\N{greek:Sigma} is an upper-case sigma.\n";
  use charnames qw(cyrillic greek);
  print "\N{sigma} is Greek sigma, and \N{be} is Cyrillic b.\n";

DESCRIPTION
Pragma "use charnames" supports arguments ":full", ":short" and script names. If ":full" is present, for expansion of "\N{CHARNAME}}" string "CHARNAME" is first looked in the list of standard Unicode names of chars. If ":short" is present, and "CHARNAME" has the form "SCRIPT:CNAME", then "CNAME" is looked up as a letter in script "SCRIPT". If pragma "use charnames" is used with script name arguments, then for "\N{CHARNAME}}" the name "CHARNAME" is looked up as a letter in the given scripts (in the specified order).

For lookup of "CHARNAME" inside a given script "SCRIPTNAME" this pragma looks for the names

  SCRIPTNAME CAPITAL LETTER CHARNAME
  SCRIPTNAME SMALL LETTER CHARNAME
  SCRIPTNAME LETTER CHARNAME
in the table of standard Unicode names. If "CHARNAME" is lowercase, then the "CAPITAL" variant is ignored, otherwise the "SMALL" variant is ignored.

CUSTOM TRANSLATORS
The mechanism of translation of "\N{...}" escapes is general and not hardwired into charnames.pm. A module can install custom translations (inside the scope which "use"s the module) with the following magic incantation:

    use charnames ();           # for $charnames::hint_bits
    sub import {
        shift;
        $^H |= $charnames::hint_bits;
        $^H{charnames} = \&translator;
    }
Here translator() is a subroutine which takes "CHARNAME" as an argument, and returns text to insert into the string instead of the "\N{CHARNAME}" escape. Since the text to insert should be different in "bytes" mode and out of it, the function should check the current state of "bytes"-flag as in:

    use bytes ();                       # for $bytes::hint_bits
    sub translator {
        if ($^H & $bytes::hint_bits) {
            return bytes_translator(@_);
        }
        else {
            return utf8_translator(@_);
        }
    }

BUGS
Since evaluation of the translation function happens in a middle of compilation (of a string literal), the translation function should not do any "eval"s or "require"s. This restriction should be lifted in a future version of Perl.